refactor: extract shared helpers, fix naming, split god file

[Wolfvin]

What this PR does

Structural refactoring of the algorithm modules, verified safe with Regrets regression testing (15 clusters, 27 outputs, 2 chains — all GREEN).

Decomposition — Split god file

sortingAlgorithms.js contained 4 sorting algorithms in one file. Split into:

• bubble-sort.js — Bubble sort only
• selection-sort.js — Selection sort only
• insertion-sort.js — Insertion sort only
• sortingAlgorithms.js — Re-exports for backward compatibility

Shared Helpers — Eliminate duplication

• Created helpers/graph-helpers.js with buildPathActions() function
• Previously, identical pathActions() was duplicated in both graph.js and shortestPath.js
• Both files now import from shared helper
• Fixed ESM import: shortestPath.js changed ./graph → ./graph.js

Naming — Make names honest and descriptive

• Fixed typo: seive() → sieve() (Sieve of Eratosthenes) with backward-compatible alias
• Fixed naming convention: convex_hull() → convexHull() (camelCase) with alias
• Descriptive names: cw() → isClockwiseTurn(), ccw() → isCounterClockwiseTurn() with aliases

---

Verification Results

All changes verified safe with Regrets output-based regression testing:

Verification	Method	Result
Clusters	All 15 .regret fingerprints still GREEN	✅ PASS
Raw Output	All 27 entry function outputs match pre-refactor baseline exactly	✅ PASS
Fingerprint Cross-check	All 15 fingerprints from new output match pre-refactor fingerprints	✅ PASS
Chain Validation	Both chain hashes match pre-refactor chains	✅ PASS

Fingerprint Summary (before → after)

Cluster	Fingerprint	Status
sieve-of-eratosthenes	61kfkvs	✅
convex-hull-graham	2ffeigp	✅
bubble-sort	dsuh6kq	✅
selection-sort	pggv13p	✅
insertion-sort	231p3bq	✅
graph-adjacency	2kqzuc0	✅
graph-weighted-adjacency	3f1bu8y	✅
connected-components	42ufcfy	✅
scc-tarjan	3cp39pq	✅
kruskal-mst	4cmle1u	✅
prim-mst	joly0qh	✅
max-flow-ek	4msj9pa	✅
dijkstra-actions	2vmdh6s	✅
bellman-ford-actions	13l9483	✅
turing-next-step	101eriz	✅

Chain Hash Summary (before → after)

Chain	Hash	Status
graph-traversal-flow	2tv6cod	✅
mst-to-sp	24sdllj	✅

No behavior was changed. All refactoring is structurally safe.